PURPOSE:The purpose of this study was to examine the association of body mass index (BMI) and aerobic fitness on cardiovascular disease (CVD) risk factors in adolescents. METHODS: The sample included 416 boys and 345 girls 9-18 y of age from the Québec Family Study. Participants were crosstabulated into four groups using a median split of age-adjusted physical working capacity (PWC) and body mass index (BMI). Group differences in age-adjusted CVD risk factors (blood pressures, fasting total cholesterol (CHOL), LDL -C, HDL-C, HDL/ CHOL, triglycerides, glucose, and a composite risk factor score) were examined by two-way ANOVA. RESULTS: Several CVD risk factors showed significant main effects for PWC, BMI and/or the PWC by BMI interaction. In general, low fit males and females had higher blood lipids and glucose compared to their high fit counterparts within BMI categories although none of the differences reached statistical significance. The high fit/low BMI group showed the best CVD risk factor profile while the low fit/high BMI showed a poorer profile as evidenced by several significant differences between these two groups. Other significant differences occurred for various risk factors between groups. CONCLUSION: Both aerobic fitness and BMI show an independent association with CVD risk factors in adolescents.

OBJECTIVE: To examine the growth status, prevalence of risk of overweight and of overweight, and secular changes in growth status in Navajo youth from 1955 to 1997. SUBJECTS: 526 (256 males, 270 females) Navajo children 6 ± 12 y of age. MEASUREMENTS: Stature and mass were measured and the body mass index (BMI) was calculated. ANALYSIS: All three variables were plotted relative to age-and sex-speci®c US reference data and the prevalence rates for risk of overweight and of overweight were estimated using the BMI as the criterion. The cut-off for the risk of overweight was the age-and sex-speci®c 85th and 95th percentiles of NHANES I, while the cut-off for overweight was a BMI 95th percentiles. Age-speci®c sex differences were compared using independent samples t-tests. Secular changes for body size were estimated by comparing age-and sex-speci®c means for stature, mass, and the BMI in the present study and two previous studies in 1955 and 1989. RESULTS: No statistically signi®cant differences were observed between sexes within age groups. In both sexes, mean age-speci®c stature appeared to be relatively stable around the 50th percentile of US reference values. Mean age-speci®c mass appeared to be relatively stable between the 50th and 90th percentiles of the reference values, while the mean BMI tended to¯uctuate about the 85th percentile. Approximately 41% of the Navajo boys and girls 6 ± 12 y of age had BMIs 85th percentiles of US reference data. Compared to corresponding data on Navajo youth in 1955 and 1989, the current sample was larger in mass and the BMI. The estimated rate of secular change in mass was about 1.5 kgadecade in younger boys and girls, and about 3 kgadecade in older boys and girls between 1955 and 1997. The estimated rate of secular change in the BMI was about 0.5 ± 1.0 unitsadecade between 1955 and 1997, while that for stature was about 2 cmadecade between 1955 and 1997. CONCLUSIONS: The results are consistent with recent ®ndings on the Navajo Health and Nutrition Survey that overweight is a serious public health concern across the lifespan in the Navajo, and that the problem begins in childhood. Furthermore, Navajo children appear to be heavier than about a decade ago.

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